Job tenure is determined by the interaction of such labor demand factors as wages, hours, working conditions, job duties and responsibilities with such labor supply factors as worker preferences and on-the-job performance. At any one point in time these factors vary from one person to the next, and at different points in time different sets of forces are likely to influence the job attachment of the same individual. Nearly all of the evidence examined indicated that a strong correlation between job tenure and age existed among males, females, Negroes, and Caucasians. Other factors which influenced job tenure were military service and compulsory and voluntary retirement. Surveys were made in 1963 and 1968 which estimated the probability of working for the same employer 5 years later of employees who had 5 to 10, 10 to 15, and 15 or more years of service. In all three length of service classes, retention rates were highest for men in their thirties or forties and lowest for those over 60 years of age. (BC)